Internet surfing is like travelling around the world – you go from country to country, town to town, shop to shop, places of interest, etc. The only difference is; you are not there in person.
Nothing is free – as the saying goes. So, while you are surfing the Internet, something just “pop-up” and offer you a “non-solicited” offer of a “free-scan” – will you accept it? After all, it is just another computer scan done by another service provider.
You may be in for a surprise! Once you allow the outsider (this service provider) to take control of your computer system, they can say what they want to say to you – like “your computer is infected with da-da-da-da number of viruses, to remove them, it will cost you $xx”. You don’t believe your computer is that bad, so you ignor the comment. Next day, you turn on your computer again, it behaves differently, worst off then before (you accepted the “free service”). You try to find the last thing you have done and to delete it – you couldn’t find or delete it.
Sometimes getting a proper anti-virus program may help to remove the problem. Sometimes you are not that lucky, you may have to get someone to re-install all the programs in your computer again. One of my friends actually got caught this way.